drivers/input/key_matrix.c

   1 /*
   2  * Manage Keyboard Matrices
   3  *
   4  * Copyright (c) 2012 The Chromium OS Authors.
   5  * (C) Copyright 2004 DENX Software Engineering, Wolfgang Denk, wd@denx.de
   6  *
   7  * See file CREDITS for list of people who contributed to this
   8  * project.
   9  *
  10  * This program is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU General Public License as
  12  * published by the Free Software Foundation; either version 2 of
  13  * the License, or (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  18  * GNU General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU General Public License
  21  * along with this program; if not, write to the Free Software
  22  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  23  * MA 02111-1307 USA
  24  */
  25
  26 #include <fdtdec.h>
  27 #include <key_matrix.h>
  28 #include <malloc.h>
  29 #include <linux/input.h>
  30
  31 /**
  32  * Determine if the current keypress configuration can cause key ghosting
  33  *
  34  * We figure this out by seeing if we have two or more keys in the same
  35  * column, as well as two or more keys in the same row.
  36  *
  37  * @param config        Keyboard matrix config
  38  * @param keys          List of keys to check
  39  * @param valid         Number of valid keypresses to check
  40  * @return 0 if no ghosting is possible, 1 if it is
  41  */
  42 static int has_ghosting(struct key_matrix *config, struct key_matrix_key *keys,
  43                         int valid)
  44 {
  45         int key_in_same_col = 0, key_in_same_row = 0;
  46         int i, j;
  47
  48         for (i = 0; i < valid; i++) {
  49                 /*
  50                  * Find 2 keys such that one key is in the same row
  51                  * and the other is in the same column as the i-th key.
  52                  */
  53                 for (j = i + 1; j < valid; j++) {
  54                         if (keys[j].col == keys[i].col)
  55                                 key_in_same_col = 1;
  56                         if (keys[j].row == keys[i].row)
  57                                 key_in_same_row = 1;
  58                 }
  59         }
  60
  61         if (key_in_same_col && key_in_same_row)
  62                 return 1;
  63         else
  64                 return 0;
  65 }
  66
  67 int key_matrix_decode(struct key_matrix *config, struct key_matrix_key keys[],
  68                       int num_keys, int keycode[], int max_keycodes)
  69 {
  70         const u8 *keymap;
  71         int valid, upto;
  72         int pos;
  73
  74         debug("%s: num_keys = %d\n", __func__, num_keys);
  75         keymap = config->plain_keycode;
  76         for (valid = upto = 0; upto < num_keys; upto++) {
  77                 struct key_matrix_key *key = &keys[upto];
  78
  79                 debug("  valid=%d, row=%d, col=%d\n", key->valid, key->row,
  80                       key->col);
  81                 if (!key->valid)
  82                         continue;
  83                 pos = key->row * config->num_cols + key->col;
  84                 if (config->fn_keycode && pos == config->fn_pos)
  85                         keymap = config->fn_keycode;
  86
  87                 /* Convert the (row, col) values into a keycode */
  88                 if (valid < max_keycodes)
  89                         keycode[valid++] = keymap[pos];
  90                 debug("    keycode=%d\n", keymap[pos]);
  91         }
  92
  93         /* For a ghost key config, ignore the keypresses for this iteration. */
  94         if (valid >= 3 && has_ghosting(config, keys, valid)) {
  95                 valid = 0;
  96                 debug("    ghosting detected!\n");
  97         }
  98         debug("  %d valid keycodes found\n", valid);
  99
 100         return valid;
 101 }
 102
 103 /**
 104  * Create a new keycode map from some provided data
 105  *
 106  * This decodes a keycode map in the format used by the fdt, which is one
 107  * word per entry, with the row, col and keycode encoded in that word.
 108  *
 109  * We create a (row x col) size byte array with each entry containing the
 110  * keycode for that (row, col). We also search for map_keycode and return
 111  * its position if found (this is used for finding the Fn key).
 112  *
 113  * @param config        Key matrix dimensions structure
 114  * @param data          Keycode data
 115  * @param len           Number of entries in keycode table
 116  * @param map_keycode   Key code to find in the map
 117  * @param pos           Returns position of map_keycode, if found, else -1
 118  * @return map  Pointer to allocated map
 119  */
 120 static uchar *create_keymap(struct key_matrix *config, u32 *data, int len,
 121                             int map_keycode, int *pos)
 122 {
 123         uchar *map;
 124
 125         if (pos)
 126                 *pos = -1;
 127         map = (uchar *)calloc(1, config->key_count);
 128         if (!map) {
 129                 debug("%s: failed to malloc %d bytes\n", __func__,
 130                         config->key_count);
 131                 return NULL;
 132         }
 133
 134         for (; len >= sizeof(u32); data++, len -= 4) {
 135                 u32 tmp = fdt32_to_cpu(*data);
 136                 int key_code, row, col;
 137                 int entry;
 138
 139                 row = (tmp >> 24) & 0xff;
 140                 col = (tmp >> 16) & 0xff;
 141                 key_code = tmp & 0xffff;
 142                 entry = row * config->num_cols + col;
 143                 map[entry] = key_code;
 144                 if (pos && map_keycode == key_code)
 145                         *pos = entry;
 146         }
 147
 148         return map;
 149 }
 150
 151 int key_matrix_decode_fdt(struct key_matrix *config, const void *blob,
 152                           int node)
 153 {
 154         const struct fdt_property *prop;
 155         int offset;
 156
 157         /* Check each property name for ones that we understand */
 158         for (offset = fdt_first_property_offset(blob, node);
 159                       offset > 0;
 160                       offset = fdt_next_property_offset(blob, offset)) {
 161                 const char *name;
 162                 int len;
 163
 164                 prop = fdt_get_property_by_offset(blob, offset, NULL);
 165                 name = fdt_string(blob, fdt32_to_cpu(prop->nameoff));
 166                 len = strlen(name);
 167
 168                 /* Name needs to match "1,<type>keymap" */
 169                 debug("%s: property '%s'\n", __func__, name);
 170                 if (strncmp(name, "1,", 2) || len < 8 ||
 171                     strcmp(name + len - 6, "keymap"))
 172                         continue;
 173
 174                 len -= 8;
 175                 if (len == 0) {
 176                         config->plain_keycode = create_keymap(config,
 177                                 (u32 *)prop->data, fdt32_to_cpu(prop->len),
 178                                 KEY_FN, &config->fn_pos);
 179                 } else if (0 == strncmp(name + 2, "fn-", len)) {
 180                         config->fn_keycode = create_keymap(config,
 181                                 (u32 *)prop->data, fdt32_to_cpu(prop->len),
 182                                 -1, NULL);
 183                 } else {
 184                         debug("%s: unrecognised property '%s'\n", __func__,
 185                               name);
 186                 }
 187         }
 188         debug("%s: Decoded key maps %p, %p from fdt\n", __func__,
 189               config->plain_keycode, config->fn_keycode);
 190
 191         if (!config->plain_keycode) {
 192                 debug("%s: cannot find keycode-plain map\n", __func__);
 193                 return -1;
 194         }
 195
 196         return 0;
 197 }
 198
 199 int key_matrix_init(struct key_matrix *config, int rows, int cols)
 200 {
 201         memset(config, '\0', sizeof(*config));
 202         config->num_rows = rows;
 203         config->num_cols = cols;
 204         config->key_count = rows * cols;
 205         assert(config->key_count > 0);
 206
 207         return 0;
 208 }